Good old fashioned American Ingenuity right there, I've seen a slew of these snow blower on roof videos in the past few days and I gotta tell you, it beats the hell out of the alternatives.
I'm not quite sure how people are getting the snow blowers up there but I think I'd rather go through the trouble of figuring that out than having a neighbor watch me lay out some panty-hose filled with salt and ammonium oxide and lay them out on my roof (or for that matter have to go through the check-out line at Target with 5 packs of panty hose, I'll just assume they call the police as soon as you exit the building when a guy makes that kind of purchase).
The other alternative is apparently hiring Department of Corrections crews to shovel your roof off. Because there is nothing that comforts me more than having a few convicted fellon crawling around on my roof or my school's roof with shovel as weapons. Seems like a wise idea.